Opaquing composition for enamels and the like.



i No Drawing.

manner.

To all whom, it may concern Be it known that I, (loser WEBER, a sub .ject ofthe King or Prussia, Gerruan Emtempts have been made to use for enameling purposes stannlc mud in the form of. a

hydrate obtained by precipitation from stannate solutions, but heretofore theseattempts have not proven successful because the hydrated stanmc oxid produced by the moth ods heretofore practised became yellow during calcination, or had only vslight covering or opaquing power. the hydrated stannic oxid, produced by precipitation from stannate solutions, has up to the present time been considered particularly injurious. Many attempts have been made to remove this alkali which adheres most tenaciously to the stannic-oXid-hydrate. lgpr" example it has been proposed that the oxid be washed with acids, or that the hydrate be calcined and then washed, The object of both of these proposals is to remove the alkali as completely as possible from the hydrated stannic oxid.

After a long series of experiments, opposed to all previous practice, it has now been established that the hydrated stannic oxid has an exceptionally good covering power for enamelim purposes if it contains a-certain amount of alkali. This hydrate'of stannic oXid can be used as a. paste a. 6. while it is still in a moist state. However, as it is not convenient to ship the hydrate while it is in this condition, it is better to dry'it be fore using it. In; drying this substance, however, care must be taken not to employ too high temperatures, say a temper-attire.

not exceeding 10014t0 C. The drying of the moist material may also be effected in a vacuum, but whatever mode of drying is employed the water of hydration must always be retained, that is, the hydrate of stannio oXid produced is one that is represented approximately by the formula SnO H,O containing about 10 per cent. of water. The

limitationfiled January 21,1912.

The alkali content of J WEBER, 0F ESSEN-ON-THE-RUHR, GERMANY.

'OIAQUING COlllIPOSI'IIGIl' FDR ENAMELS AND THE LIKE.

Patented Aug. it, 1915 Serial No. 6%,500.

product may also contain several per cent. more water than this.

In the treatment of the precipitated bydrate care should be taken to Wash the hydrate only moderately, and it is also important that, for'the purpose of washing, Water, preferably cold water, but no acid be used, in order that the product may retain the desired content of alkali; This alkali cannot be wholly separated from the hydrate even by washing with water, and it seems proper to regard the combination of this alkali with the hydrate of stannic oXid as a complex chemical compound. The percentage of chemically combined alkali seams to amount in nearly all cases to about 4.2 per cent. Na O.

Numerous experiments in enameling have established the surprising fact that when the alkali is removed, for example by means of acids, the covering power of the material gradually decreases to such an extent that the stannic oxid is no longer useful for enameling purposes. The covering power lecreases in proportion to the decrease in the alkali content, that is to say, the greater the amount of alkali removed, as for instance by treatment with acids, the greater the decrease in the covering power. It follows from the foregoing that a proper percentage of alkali, such .as previously mentioned, in combination with a high percentage of water isthe characteristic feature of stannic oxid having good covering power.

It is important to note that even treatment with cold, diluted acid is injurious to the product as soon as a point is reached. at which considerable quantities of alkali are removed by such acid. The covering power of the product is also decreased by treating it with hot water, or by boiling it, or by drying it after washing to such an extent that the hydrate containing about 10 per cent. of Water loses a considerable portion of its water content.

Clomparative experiments made with the oxid of tin heretofore used and with this product have established that the product obtained in the manner hereinbefore described and containing only about 80-85 per cent. of 8110,, about 8&4 per cent. of water, and in addition, 35 per cent. of alkali, has a stronger covering power than the oxid of tin on the market, and manufactured up to the present time according to the old combustion process, which oxid of tin contains nearly 100 per cent. of S110 Acolnparison of the amount of tin (in the form of its oxid) necessary to'obtain the same covering power, shows that 70 parts of the new prodnot give the same effect as 100 parts of the oxid heretofore used, produced by thKfiombustion of tin.

In View of the fact that the hydrated stannic oxid above described is produced with less labor and expense, and that it has much greater covering power than the oxid produced by the old-combustion process, and in view of the further fact that the new product has proven to be cheaper, owing to its greater covering power, than the stannic oxid marketable heretofore, the present invention represents an important technical improvement.

The product above described can be obtained from stannate solutions of all kinds, but; since for enameling purposes anoxid of tin as pure as possible and free from other metals must be employed; it is best to start from '"pure stannate solutions.

What I claim is:

1. An opaquing composition for enamels and the like comprising hydrated stannie ox'id and from three to five per cent. of alkali.

2. An opaquing composition for enamels and the like comprising stannic oXid eont aining about ten per cent. of Water and from three to five per cent. of alkali.

In witness whereof I have hereunto set my hand in the presence of tWo witnesses.

lVitnesses HELEN NUEER, ALBERT NUFER.

JOSEF WEBER. 1.3.1 

